JP3698840B2 - Piezoelectric vibrator for piezoelectric vibration gyro - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a piezoelectric vibrator for a piezoelectric vibration gyro that belongs to a gyroscope mainly used in an automobile navigation system or a camera shake correction device for a camera-integrated VTR camera, and more specifically, as a vibration mode. The present invention relates to a piezoelectric vibrator for a piezoelectric vibration gyro using an energy confinement vibration mode.
[0002]
[Prior art]
Conventionally, a piezoelectric vibration gyro belongs to a gyroscope using a mechanical phenomenon in which when a rotational angular velocity is applied to a vibrating object, a Coriolis force is generated in a direction perpendicular to the vibration direction.
[0003]
In general, when a piezoelectric vibration gyro is rotated in a state where vibration is excited on one input side in a complex vibration system configured to be able to excite and detect two directions orthogonal to each other, By the action of the Coriolis force described above, a force acts in a direction perpendicular to the vibration, and the vibration is excited on the other output side. Here, since the magnitude of the vibration excited on the output side is proportional to the amplitude (magnitude) of the vibration on the input side and the rotation angular velocity of the piezoelectric vibrator, the vibration amplitude (driving voltage) on the input side is made constant. In this case, the magnitude of the applied rotational angular velocity can be obtained from the magnitude of the output voltage (detection voltage) obtained from the output side.
[0004]
FIG. 4 is a perspective view showing a basic configuration of a conventional piezoelectric vibrator 100 for a piezoelectric vibration gyro. In this piezoelectric vibrator 100, piezoelectric ceramic thin plates 102 and 103 are bonded to substantially the center of adjacent surfaces of a metal prism 101 having a square cross-sectional shape. These piezoelectric ceramic thin plates 102 and 103 are respectively formed with electrodes on both surfaces and polarized in the thickness direction, and lead terminals 104 and 105 for lead-out are formed on one surface (surface).
[0005]
It is known that the metal prism 101 having a square cross section has two bending vibration modes orthogonal to each other, and the resonance frequencies of the two bending vibration modes are substantially equal when the material characteristics are uniform. Accordingly, when a voltage having a frequency substantially equal to the resonance frequency of the bending vibration of the metal prism 101 is applied to the piezoelectric ceramic thin plate 102, the piezoelectric ceramic 102 is bent and vibrated in a direction (y-axis direction) where the surface on which the piezoelectric ceramic 102 is bonded becomes uneven. When the metal prism 101 is rotated around an axis (z axis) parallel to the length direction in this state, the metal prism 101 is in a direction (x-axis) where the surface on which the piezoelectric ceramic thin plate 103 is joined is corrugated by the action of the Coriolis force. Direction) and a voltage is generated in the piezoelectric ceramic thin plate 103 by such a piezoelectric effect.
[0006]
The magnitude of the voltage generated here is proportional to the magnitude of the vibration excited by the piezoelectric ceramic thin plate 102 and the magnitude of the applied rotational angular velocity. Therefore, if the magnitude of the excitation voltage applied to the piezoelectric ceramic thin plate 102 is constant, the voltage generated in the piezoelectric ceramic thin plate 103 becomes a voltage proportional to the rotational angular velocity of the metal prism 101.
[0007]
By the way, an oscillator having a structure using an energy confinement vibration mode (hereinafter simply referred to as an energy confinement type oscillator) is used for an intermediate frequency filter of FM radio or television.
[0008]
FIGS. 5A and 5B show a basic configuration of a conventional energy confinement type vibrator. FIG. 5A shows a plan view thereof, and FIG. 5B shows a sectional view thereof.
[0009]
Here, the energy confinement vibration indicates a vibration mode in which vibration energy is concentrated in the vicinity of the drive electrode. This includes longitudinal vibration and sliding vibration in the thickness direction of the piezoelectric plate 10 as well as piezoelectric vibration. There are vertical vibration and sliding vibration of a rectangular plate.
[0010]
Referring to FIGS. 5 (a) and 5 (b), the energy confinement vibration is concentrated in the vicinity of the drive electrode because the vibration energy is concentrated. For example, as shown in FIG. Using the piezoelectric plate 10 having a thickness of 6 mm and a thickness of 0.2 mm, the drive electrodes 51 and 52 are formed in a region having a diameter of 1.5 mm substantially at the center of one main surface, and the drive electrodes 51 and 52 are formed on the other main surface. Suppose that a drive electrode 53 is formed in a region extending from a portion facing 52 to obtain a 10.7 Mhz ceramic filter for FM radio.
[0011]
As shown in FIG. 6, the support structure of the ceramic filter (energy confinement type vibrator) in this case is such that cavities 54 are formed on both sides of a region having a diameter of about 3 mm with the drive electrodes 51, 52, 53 as the center. Other portions may be fixed with the resin 55. Even such a structure hardly affects the vibrator characteristics. That is, in the case of this energy confinement type resonator, the lead terminal can be freely formed, and a filter that is not affected by the support structure can be obtained.
[0012]
[Problems to be solved by the invention]
In the case of the piezoelectric vibrator for piezoelectric vibration gyro shown in FIG. 4 described above, since the bending vibration mode of the metal prism is used, the piezoelectric vibrator must be supported and fixed at the position of the vibration node. The work is complicated, and when connecting the drive / detection circuit and the electrode of the piezoelectric vibrator with the lead wire in the manufacturing process of assembling the piezoelectric vibration gyro, if the connection state varies, the gyro characteristics will vary. Connections must be made with high accuracy so that variations can be suppressed. However, such connection work is difficult, and a piezoelectric vibrator supported by a holder is placed on a board on which drive and detection circuits are installed. Because of the assembly, there is a problem that it is difficult to construct a small and thin piezoelectric vibration gyro.
[0013]
On the other hand, in the case of the energy confinement type piezoelectric vibrator shown in FIGS. 5A and 5B, such a problem is solved, and the input / output terminals can be connected without using lead wires. In addition, it is assumed that it is easy to configure a piezoelectric vibration gyro by combining a piezoelectric vibrator on a substrate on which a drive / detection circuit is arranged. Since the detailed configuration is not for a piezoelectric vibration gyro, there is a problem that it cannot be applied as it is.
[0014]
The present invention has been made to solve such problems, and its technical problem is that input / output terminals can be connected without using lead wires, and a small and thin configuration with a simple configuration. An object of the present invention is to provide a piezoelectric vibrator for an energy confinement type piezoelectric vibration gyro capable of easily manufacturing a piezoelectric vibration gyro.
[0015]
[Means for Solving the Problems]
According to the present invention, a piezoelectric plate having a polarization axis in the thickness direction, a first counter electrode formed to be opposed to a substantially central portion of one main surface of the piezoelectric plate at a predetermined interval, and a piezoelectric plate A second counter electrode formed at a substantially central portion of one main surface and opposed to the first counter electrode at a predetermined interval at a position rotated by 90 degrees; and the other main electrode of the piezoelectric plate An extending direction of the first counter electrode and the second counter electrode at an approximately central portion of the surface at a position opposed to the region where the first counter electrode and the second counter electrode are formed; Includes a third counter electrode extending in a direction deviated by 45 degrees and opposingly formed at a predetermined interval. Further, an excitation voltage is applied between the third counter electrodes, Detecting a voltage difference between output voltages generated between the first counter electrode and the second counter electrode when rotated around an axis orthogonal to one main surface and the other main surface In the piezoelectric vibrator for piezoelectric vibration gyro constructed as described above, the piezoelectric vibrator for piezoelectric vibration gyro in which the distance between the third counter electrodes is larger than the distance between the first counter electrode and the second counter electrode is obtained. It is done.
[0016]
Furthermore, according to the present invention, in the piezoelectric vibrator for a piezoelectric vibration gyro, the piezoelectric vibration gyro for the piezoelectric plate in which only the vicinity of the region where the second counter electrode is formed from the first counter electrode on the piezoelectric plate is polarized in the thickness direction. A piezoelectric vibrator is obtained.
[0017]
In addition, according to the present invention, in any one of the piezoelectric vibrators for a piezoelectric vibration gyro, a piezoelectric vibrator for a piezoelectric vibration gyro using a piezoelectric ceramic as a piezoelectric plate can be obtained.
[0018]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, the piezoelectric vibrator for piezoelectric vibration gyro of the present invention will be described in detail with reference to the drawings.
[0019]
FIG. 1 is a perspective view showing a basic configuration of a piezoelectric vibrator 1 for energy confinement type piezoelectric vibration gyro according to one embodiment of the present invention.
[0020]
The piezoelectric vibrator 1 includes first counter electrodes 11a and 11b formed to face a piezoelectric plate 10 having a polarization axis in the thickness direction at a substantially central portion of one main surface with a predetermined interval. The second counter electrodes 12a and 12b, which are substantially central portions of one main surface and are opposed to each other at a predetermined interval at a position rotated by 90 degrees with respect to the first counter electrodes 11a and 11b. These counter electrodes extend in the substantially central part of the other main surface at positions facing each other between the regions where the first counter electrodes 11a and 11b and the second counter electrodes 12a and 12b are formed. It includes third counter electrodes 13a and 13b (shown by broken lines) formed extending in a direction deviated from the direction by 45 degrees.
[0021]
However, in this piezoelectric vibrator 1, an excitation voltage is applied between the third counter electrodes 13a and 13b, and the piezoelectric plate 10 is rotated around one main surface and an axis orthogonal to the other main surface. Sometimes it is configured to detect a voltage difference between output voltages generated between the first counter electrodes 11a and 11b and between the second counter electrodes 12a and 12b. That is, here, the third counter electrodes 13a and 13b are for vibration drive, and the first counter electrodes 11a and 11b and the second counter electrodes 12a and 12b are for vibration detection.
[0022]
Further, when the distance between the first counter electrode 11a, 11b and the second counter electrode 12a, 12b and the third counter electrode 13a, 13b is short, these counter electrodes are connected to the drive / detection circuit to be connected to the potential. Is fixed, the electrolysis direction is disturbed and it becomes difficult to drive and detect the slip vibration in the energy confinement vibration mode. To avoid this, the distance between the third counter electrodes 13a and 13b is set to the first pair. The distance between the electrodes 11a and 11b and the distance between the second counter electrodes 12a and 12b are made larger, so that the potential connected to the third counter electrodes 13a and 13b hardly affects the energy confinement vibration mode. Yes.
[0023]
Further, here, piezoelectric ceramic is used for the piezoelectric plate 10, and only the vicinity of the region of the piezoelectric plate 10 where the second counter electrodes 12a and 12b are formed from the first counter electrodes 11a and 11b is polarized in the thickness direction. ing.
[0024]
The driving principle of the piezoelectric vibrator 1 will be described in detail later, but an excitation AC voltage having a frequency substantially equal to the resonance frequency of the thickness-slip mode of the piezoelectric plate 10 is applied between the third counter electrodes 13a and 13b. Then, in the region where the third counter electrodes 13a and 13b are opposed, the sliding vibration of the energy confinement vibration mode is generated in the direction in which the counter electrodes 13a and 13b are opposed. In this state, when the piezoelectric plate 10 is rotated around an axis orthogonal to the main surface, thickness shear vibration is generated in a direction perpendicular to the direction of the thickness shear vibration mode excited by the action of the Coriolis force.
[0025]
A voltage is generated between the first counter electrodes 11a and 11b and between the second counter electrodes 12a and 12b by the thickness shear vibration generated by the Coriolis force, but is generated at the first counter electrodes 11a and 11b. The voltage generated at the second counter electrodes 12a and 12b is ± 45 degrees with respect to the direction of the thickness-shear vibration in which each counter electrode (11a, 11b, 12a, 12b) is excited. Since the directions are deviated, the voltages have the same amplitude and are different in phase by 180 degrees.
[0026]
Therefore, by detecting the voltage difference between these output voltages and synchronously detecting this voltage at a predetermined timing, an output voltage proportional to the applied rotational angular velocity can be obtained.
[0027]
That is, in the piezoelectric vibrator 1, as described above, the distance between the third counter electrodes 13a and 13b for driving vibration is set to the distance between the first counter electrodes 11a and 11b for detecting vibration and the second counter electrode. Although the potential of the drive electrode is hardly affected by the output of the detection electrode by setting it to be larger than the interval between 12a and 12b, in addition to this, when piezoelectric ceramic is used as the piezoelectric plate 10, the first Only the vicinity of the region where the second counter electrodes 12a and 12b are formed from the counter electrodes 11a and 11b in the thickness direction is polarized in the thickness direction, so that unnecessary vibration is not generated in the region where each counter electrode (11a, 11b, 12a, 12b) faces. This is also an important factor because it makes it possible to excite high-precision energy confinement vibrations without noise.
[0028]
Next, the principle of operation of such a piezoelectric vibrator for energy confinement type piezoelectric vibration gyro will be described in more detail.
[0029]
FIG. 2 shows a basic configuration of a thickness-slip energy confinement type piezoelectric vibrator when the piezoelectric vibrator for a piezoelectric vibration gyro described above is simplified. FIG. 2 (a) relates to a plan view thereof. (B) relates to the side sectional view. FIG. 3 shows the displacement distribution in the thickness direction (z-axis direction) of the thickness-slip energy confining piezoelectric vibrator shown in FIG.
[0030]
This thickness-slip energy confining type piezoelectric vibrator is called a parallel electrolytic excitation type, and is a portion facing in the x-axis direction on the same surface of the central portion of the piezoelectric plate 10 polarized in the thickness direction (z-axis direction). Electrodes 14a and 14b are formed. Since an electric field in a direction (x-axis direction) substantially parallel to one surface of the piezoelectric plate 10 is applied to a portion sandwiched between these partial electrodes 14a and 14b, polarization in a thickness direction orthogonal to the electric field and If the dimensions of the partial electrodes 14a and 14b are appropriately set according to the characteristics of the piezoelectric material using the interaction, a parallel electric field excitation type thickness-slip energy confining piezoelectric vibrator can be formed in this part.
[0031]
When the thickness-slip energy confinement type piezoelectric vibrator is resonating at a half wavelength, the displacement distribution in the thickness direction is as shown in FIG. 3 with the x-axis, y-axis, and z-axis shown in FIG. The displacement is parallel to the plate surface of the piezoelectric plate 10 and the wave propagation direction is the thickness direction of the piezoelectric plate 10 (z-axis). Direction)).
[0032]
【The invention's effect】
As described above, according to the piezoelectric vibrator for a piezoelectric vibration gyro of the present invention, an existing energy confinement type piezoelectric vibrator is modified to a structure for a piezoelectric vibration gyro, and the electric potential of the drive electrode is equal to that of the detection electrode. As input / output terminals can be connected without using lead wires as an electrode pattern that is not easily affected by output, there is almost no effect on the gyro characteristics due to support and fixation, and it is possible to support it firmly. A small and thin piezoelectric vibration gyro with excellent vibration resistance and impact resistance can be easily manufactured with a simple configuration.
[Brief description of the drawings]
FIG. 1 is a perspective view showing a basic configuration of a piezoelectric vibrator for an energy confinement type piezoelectric vibration gyro according to an embodiment of the present invention.
FIG. 2 shows a basic configuration of a thickness-slip energy confinement type piezoelectric vibrator when the piezoelectric vibrator for a piezoelectric vibration gyro shown in FIG. 1 is simplified, (a) relates to a plan view thereof, (b) ) Relates to the side sectional view.
3 shows a displacement distribution in the thickness direction (z-axis direction) of the thickness-slip energy confinement type piezoelectric vibrator shown in FIG. 2. FIG.
FIG. 4 is a perspective view showing a basic configuration according to an example of a piezoelectric vibrator for a conventional piezoelectric vibration gyro.
FIGS. 5A and 5B show a basic configuration of a conventional energy confinement type vibrator, in which FIG. 5A relates to a plan view and FIG. 5B relates to a side sectional view thereof.
6 is a side view showing a support structure of the energy confinement type vibrator shown in FIG. 5. FIG.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1,100 Piezoelectric vibrator 10 Piezoelectric plate 11a, 11b 1st counter electrode 12a, 12b 2nd counter electrode 13a, 13b 3rd counter electrode 14a, 14b Partial electrode 51, 52, 53 Drive electrode 54 Cavity part 55 Resin Layer 101 Metal prism 102, 103 Piezoelectric ceramic thin plate 104, 105 Lead terminal

Claims (3)

  A piezoelectric plate having a polarization axis in the thickness direction; a first counter electrode formed at a substantially central portion of one main surface of the piezoelectric plate at a predetermined interval; and one main surface of the piezoelectric plate A second counter electrode formed opposite to the first counter electrode at a predetermined interval at a position rotated by 90 degrees with respect to the first counter electrode, and the other main surface of the piezoelectric plate An extending direction of the first counter electrode and the second counter electrode in a substantially central portion at a position opposite to a region where the first counter electrode and the second counter electrode are formed; Includes a third counter electrode extending in a direction deviated by 45 degrees and opposingly formed at a predetermined interval, further applying an excitation voltage between the third counter electrodes, When the plate is rotated about an axis perpendicular to the one main surface and the other main surface, the first counter electrode and the second counter electrode generate. In a piezoelectric vibrator for a piezoelectric vibration gyro configured to detect a voltage difference between output voltages of the first and second counter electrodes, the distance between the third counter electrode and the second counter electrode A piezoelectric vibrator for a piezoelectric vibration gyro characterized by being larger than the interval.   2. The piezoelectric vibrator for a piezoelectric vibration gyro according to claim 1, wherein only the vicinity of a region where the second counter electrode is formed from the first counter electrode of the piezoelectric plate is polarized in the thickness direction. Piezoelectric vibrator for piezoelectric vibration gyro.   3. A piezoelectric vibrator for a piezoelectric vibration gyro according to claim 1, wherein the piezoelectric plate is made of piezoelectric ceramics.

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